Asthma

What is asthma?

Asthma is a common chronic condition of the airways.

People with asthma experience episodes of wheezing, shortness of breath, coughing and chest tightness due to widespread narrowing of the airways. The symptoms of asthma vary over time and may be present or absent at any point in time [1]. Asthma affects people of all ages and has a substantial impact on the community. In Australia, asthma accounted for 29% of the total burden of disease due to respiratory conditions in 2011 [2].

The symptoms of asthma are usually reversible, either with or without treatment. The severity of asthma ranges from mild, intermittent symptoms, causing few problems for the individual, to severe and persistent wheezing and shortness of breath. In a few people with asthma, the disease has a severe adverse impact on quality of life and may be life-threatening.

While the underlying causes of asthma are still not well understood, there are a number of genetic, environmental and lifestyle factors that may increase the risk of developing asthma.

A number of factors can trigger asthma symptoms, and triggers may differ between individuals.

Triggers for asthma symptoms may include:

viral respiratory infections, such as colds

exercise

exposure to specific allergens (if a person is allergic to them) such as:

house dust mites

pollens

mould spores

pets and animals

environmental irritants such as:

tobacco smoke and other air pollutants

cold/dry air

dietary triggers such as:

food chemicals/additives (if a person is intolerant)

medicines such as:

aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs)

occupational exposures to:

specific allergens

dust

fumes.

It can be difficult to distinguish asthma from Chronic Obstructive Pulmonary Disease (COPD) because the symptoms of both conditions can be similar – both are chronic inflammatory diseases that involve the small airways and cause airflow limitation [3]. Although the current definitions of asthma [4] and COPD [5] overlap, there are some important features that distinguish typical COPD from typical asthma. For example, people with COPD continue to lose lung function despite taking medication, which is not a common feature of asthma. More information and reports on COPD can be found in the COPD snapshot.

There is increasing recognition of asthma-COPD overlap (also called asthma-COPD overlap syndrome, or ACOS), which affects around 15–20% of people with either diagnosis [6,7]. It is important to identify people with asthma-COPD overlap, because they are at higher risk than patients with asthma or COPD alone, and because they should be treated differently from people with asthma or COPD alone [8]. The National Asthma Council Australia & Lung Foundation recently released an information paper on Asthma-COPD overlap, which includes recommendations for the treatment and management of the condition [8].

Who gets asthma?

11% of the Australian population have asthma.

Around 2.5 million Australians (11% of the total population) have asthma, based on self-reported data from the 2014–15 Australian Bureau of Statistics (ABS) National Health Survey (NHS) [9]. In children, aged 5─14 years, asthma is a leading cause of total burden, with asthma being the top ranked leading cause of total burden for male children aged 5─14 and the second leading cause of total burden for female children aged 5─14 [10].

Prevalence by age and sex

Based on the 2014–15 AHS, among those aged 0–14, asthma was more common in males, but among those aged 15 and over, asthma was more common in females (Figure 1). This change in prevalence for males and females after adolescence is likely due to a complex interaction between changing airway size and hormonal changes that occur during adolescent development. This change in prevalence for males and females after adolescence is likely due to hormonal changes during adolescent development and differences in environmental exposures [11].

Figure 1: Prevalence of asthma, by age and sex, 2014–15

Note: Includes self-reported doctor-diagnosed current and long-term asthma.

How does asthma affect quality of life?

Asthma is associated with poorer quality of life, with disease severity and the level of control both having an impact.

Asthma has varying degrees of impact on the physical, psychological and social wellbeing of people living with the condition. People with asthma are more likely to report a poor quality of life. This is more pronounced among people with severe or poorly controlled asthma [13,14].

Asthma is described as well-controlled when there are few symptoms and little reliever use (e.g. less than 3 days/week), and no night waking or limitation of activity. A 2012 survey of 2,686 Australians aged 16 years and older with current asthma found that asthma was not well-controlled in 45% of people with current asthma. More than half of this group were not using a preventer inhaler, or were using it infrequently [15].

In 2014–15, self-assessed health was, on average, worse among people with asthma, compared with people without the condition. People with asthma were less likely to report excellent health, and more likely to report fair or poor health [9].

Figure 1: Self-assessed health among people with and without asthma, ages 15+, 2014–15